Upgrading to 120gb Hard Drive?

I'm considering ordering a used 120gb hdd off Amazon.com. It comes with a transfer kit and I don't mind if it's black. I just need more space because my 20gb isn't cutting it. Will I encounter any problems ordering it used?

if i was u id wait i have a feeling that they are gonna realease a 250gb (because of the MW pack and forza 3 pack)

and maybe prices drop alil